Auto Eject of Install Disc

I was testing out my Mac OS X Leopard install disk (v 10.5 Family Pack) in anticipation of erasing and reformatting my hard drive. Once slotted in, the CD/DVD drive does all its usual noises but then automatically ejects the disk.

I have a MacBook 2,1 - 2Ghz, 1GB RAM, running OS 10.5.8.
The disk image never shows up on my desktop display.
The Install DVD reads and works fine on my other computer (a Mac Mini).
Other DVDs read and work fine on the MacBook.

Any ideas as to why this particular (and rather vital!) disk isn't working and how I can get it to work?

Thanks,

JY

Message was edited by: jytessier